package 中等;

public class 把二叉搜索树转换为累加树 {


    int sum = 0;

    public TreeNode convertBST(TreeNode root) {
        if (root == null){
            return null;
        }

        convertBST(root.right);
        sum += root.val;
        root.val = sum;
        convertBST(root.left);
        return root;
    }

}
